As a method for smelting nickel oxide ore called limonite or saprolite, a method of dry smelting that produces nickel matt using a flash smelting furnace, a method of dry smelting that produces ferronickel using a rotary kiln or moving hearth furnace, a method of wet smelting that produces a mix sulfide using an autoclave, etc. have been known.
Upon charging the nickel oxide ore to the smelting step, pre-processing is performed for pelletizing, making into a slurry, etc. the raw material ore. More specifically, upon pelletizing the nickel oxide ore, i.e. producing pellets, it is common to mix components other than this nickel oxide ore, e.g., binder and reducing agent, then further perform moisture adjustment, etc., followed by charging into agglomerate producing equipment to make a lump on the order of 10 to 30 mm, for example (indicated as pellet, briquette, etc.; hereinafter referred to simply as “pellet”).
It is important for this pellet to maintain the shape thereof even if the smelting operations such as charging into a smelting furnace (reducing furnace) and reducing and heating is begun in order to achieve the roles such as preserving breathability and prevention of uneven distribution of raw material components, for example.
For example, Patent Document 1 discloses, as a pre-treatment method upon producing ferronickel using a moving hearth furnace, technology of producing pellets by adjusting surplus carbon content of the mixture in a mixing step to make a mixture by mixing raw materials including nickel oxide and iron oxide with carbonaceous reducing agent and charging these pellets into a furnace to perform a reduction step.
However, the carbonaceous reducing agent has poor “closeness” with other raw materials, and when comparing with a case of not adding carbonaceous reducing agent, the strength of the produced pellet weakens. Upon charging pellets into the smelting furnace, in the case of the strength of pellets being insufficient so much as to break down with the force received upon charging, there is a problem in that some kind of means for obtaining the required strength must be devised such as adding binder, as in the description in the aforementioned Patent Document 1 (e.g., refer to paragraph [0061]).
Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2004-156140